Polykastro is a small town in the regional unit of Kilkis, northern Greece. It is located on the Axios plain near the border with North Macedonia and serves as an important transport and trade hub.

The area has a strong agricultural character, with extensive farmland in the fertile plain, while the town provides basic infrastructure, schools, and a local market serving the wider Paionia region.

Polykastro functions as a strategic transit point toward the northern borders and acts as a center for the surrounding settlements.